Ester oils and process for their preparation



United States Patent {Office 3,006,937 Patented Oct. 31, 1961 3,006,937ESTER OHJS AND PROCESS FUR THEE PREPARATION Karl Biichner,Duisburg-Hamborn, and Heinrich Schwarz,

()herhausen-Sterkrade, Germany, assignors to RuhrchernieAktiengesellschaft, Oberhausen-Holten, Germany, a corporation of GermanyNo Drawing. Filed Dec. 15, 1953, Ser. No. 398,416 Claims priority,application Germany Dec. 18, 1952 14 Claims. (Cl. 260-410) Thisinvention relates to new and useful improvements in ester oils.

One object of the invention is valuable ester oils having a low pourpoint. This, and still further objects will become apparent from thefollowing description:

In accordance with the invention it has been found that esters having ahydroaromatic component and an aliphatic component constitute valuableoils which have a low, pour point. These oils have proven particularlysuitable as clock-work oil or lubrication oil for ice machines, andother machines and apparatus which operate at low temperature. The oilshave also proven particularly valuable when used alone or in mixture, ascirculating oils for turbines or for breaking-in oils for internalcombustion engines. Depending upon the chain length of the aliphaticester portion, the flash point of these oils may be adjusted to theparticular level desired, while the pour point, especially in the caseof high-molecular weight aliphatic portions, may be kept low by chainbranching.

The ester oils in accordance with the invention may be esters ofhydroaromatic alcohols and aliphatic carboxylic acids or ofhydroaromatic carboxylic acids and aliphatic alcohols. It has been foundthat if the carbonyl group in the ester is located on the aliphaticside, i.e., the esters are esters of aliphatic carboxylic acids andhydroaromatic alcohols, particularly good viscosity indexes will beobtained.

The hydroaromatic ester components are preferably obtained by thecatalytic addition of water gas to terpene hydrocarbons (C H as, forexample, are available in turpentine oil.

The catalytic addition of water gas, i.e., carbon monoxide and hydrogento the terpene hydrocarbons is the conventional aldehyde synthesis andis effected, for example, with cobalt catalysts. The catalysts, gaspressures and temperatures used therein are those as known to any expertfamiliar with the Oxo synthesis or hydroformylation (see, for example,US. Patents 2,327,- 066, 2,497,303; U.K. Patent 614,010; FIAT Report No.1000; Petroleum Processing, February 1953, pp. 241- 248). The startingterpene hydrocarbon may constitute the total terpenes or individualfractions of a narrow boiling range. When individual fractions are used,the same may be processed or pretreated with catalysts in theconventional manner for the purpose of rearrangement or cyclization.

The addition products from the catalytic water gas addition may beconverted into carboxylic acids or alcohols.

The addition products may be converted into carboxylic acids byoxidation, as, for example, with air or oxygen, or may be converted intocarboxylic salts by the addition of mild alkali. The carboxylic acidsmay be recovered from these salts in the known manner.

The addition products may be converted into alcohols by catalyticallyhydrogenating the same, or, if desired, by using a hydratinghydrogenation in the known manner for obtaining a higher yield. Thealcohols may be used as such or may be converted into correspondingcarboxylic acids by treatment with alkali at the melting temperature inthe conventional manner.

The starting materials of the process according to the By the catalyticaddition of water gas (Oxo synthesis) followed by hydrogenation, thereis fdrmed therefrom the terpanol (camphanol) having the followingstructural formula:

It is possible by oxidation to recover from terpanol of the abovestructure the terpane-carboxylic acid (camphane carboxylic acid) havingthe following structural formula:

The dipentene which is isomeric with the camphene has the followingstructural formula:

Herefrom, by the catalytic addition of water gas followed byhydrogenation, an isomeric terpanol (menthane-methylol) is recoveredhaving the following structural formula:

Herefrom, by oxidation, the corresponding terpane carboxylic acid may berecovered which has the following stru tural formula:

water gas to the terpene hydrocarbon by treatment with oxygen or air, ifnecessary or desired, in the presence of mild alkali, such as soda. Whenusing the hydroaromatic 1 component in the form of a carboxylic acid,the aliphatic 5 component must, of course, be in the form of an alcohol.H2O CH1 The same considerations should be given when choosing 3; thealcohol as indicated above for the aliphatic carboxylic acid. Thus,branched aliphatic alcohols should be used HG 1n the case of long-chaincompounds in order to keep the pour point low. Branched alcohols of thistype are H2O CCOOH Obtained, for example, by the catalytic addition ofcarbon H monoxide and hydrogen to olefins, followed by a catalytic Ifthe hydroaromatic portion is present as an alcohol, treatment withhydrogen if in the fractional distillation fatty acids must, of course,be used for the esterification. of the hydrocarbon-alcohol mixtures thefirst third or first Alcohols or carboxylic acids of the molecular sizeC four-tenths of the distillate are collected separately from to C andpreferably 0., to C areu sed for the esterificathe remainder. Theintermediate fraction obtained betion. The esterification is effected bymethods known to tween the hydrocarbon fraction and the alcohol may alsoany expert which is familiar with the esterification of orbe used forthe production of the ester oils of low pour ganic compounds. Theesterification conditions used point in accordance with the invention.Esters thus may be seen in detail from the following examples. The 20produced, however, have the carbonyl group separated use of short-chainacids results in esters of low viscosity by an oxygen bridge on thehydroaromatic ester side. having flash points of about l17-150 C.; pourpoints As indicated in Examples 5, 6, and 7 of the following below 60C., and high viscosity indexes. The characexamples, esters of this typeexhibit a poorer viscosity teristics of such esters are as follows:index, and their flash points are lower by 10-20" C. than Density noEster Pour Flash Viscosity Viscosity at 20 0. number pointG. point0. at0. index Terpane methylol/ester acetic acid. 0. 965 1. 4640 264 66 117l. 44 +155 Terpane methylolpropionic acid ester. 0. 958 l. 4634 248 68124 1. 43 +164 Terpane methylolbutyric acid ester. 0. 947 l. 4631 234-70 129 1. 51 +152 Terpane methylolvaleric acid ester- 0. 939 l. 4612220 68 144 1. 64 +148 Terpane methylolcaproic acid ester- 0. 93 l. 4631202 -71 153 1. 77 +157 If the esterification is effected with long-chainfatty those of the corresponding esters produced from terpane acids,ester oils of increased viscosity and having flash methylol and branchedfatty acids. points which range above 200 C., are obtained. The Theesters themselves may be distilled under reduced viscosity index ofthese oils ranges above 125. The pour pressure without decomposition andare easily obtained points of these oils, however, are relatively high,so that in this manner in pure form. the same are not high-gradelubricating oils. For ex- The following examples are given by way ofillustraample, the stearic ester of terpane methylol C H O has tion andnot limitation: the following characteristics: Example 1 :23:32 igf;;'2?;"': 336 grams (2 mols) rp e y l hHmO, which Ester number D 124(129) had been obtained from turpentine oil by the catalytic H h 'Z'addition of water gas and by hydrogenation, were boiled as point 216 130nh d 1 h Viscosity at 30 C E l 4 7 [Wlt gral'ns ace 1c a Y nconcentrated Y drochloric acid and 150 cc. benzene for 2 hours under aViscosity index 138 Pour point C +12 reflux condenser with waterseparator. Thereafter, the raw product was Washed three times with theSame If, instead of unbranched fatty acids, branched chain volume ofwater and the benzene was distilled off. A fatty acids are used, as, forexample, a branched C fatty raw ester having the followingcharacteristics was obacid, then ster oils are obtained which meet allthe retained:

uirements of the highest grade lubricants. An ester iiibricating oil ofthis kind has the following characterisg i ties for example: Ster Hum 55(calculated: 267).

Hydroxyl number 0. Density at 20 C 0.910 Density at 20 C 0.965.Refractive index, n 1.4666 Refractive index, n 1.4632. Viscosity:Molecular weight 204 (calculated: 210). 2: a g Engler fi Distillationresulted in a Water-White ester havin a At bolhng point of l19132 C. at10 mm. Hg and having the followin characteristics- Flash pomt C.-- 218Pour point C. 58 65 Acid number 0. Viscosity index s er number 264(calculated: 267). Saponification number 136 Hydroxyl number 0.Molecular weight 390 Density at 20 C 0.965.

Refractive index, n 1.4640. If the hydroaromah'c c mp f h er 1s 1n theMolecum weight 212 (calculated, 210) form of the acid, then, instead ofthe terpane methylol, 7 p point s C the corresponding terpane carboxylicacid C H O may Flash point C be used. This terpane carboxylic acid maybe obtained Viscosity index as an oxidation product of the terpanemethylal. The m terpane carboxylic acid may also be obtained from theExample 2 terpane methylal formed by the catalytic addition of the 75The same mixture as used in Example 1 was used for the esterificationwith the exception that 180 grams commercial propionic acid were usedinstead of 130 grams acetic anhydride. During the esterification, aquantity of propionic acid equivalent'to the acid content of theseparated water was added. After the distillation, a water-white esterboiling between 129 and 141 C. at 10 mm. Hg, and having the followingcharacteristics, was obtained:

Acid number Ester number 248 (calculated: 250). Hydroxyl number 0.Density at 20 C 0.958. Refractive index, 11 1.4634. Molecular weight 220(calculated: 224). Pour point 68 C. Flash point 124 C. Viscosity index164.

Example 3 The same mixture as used in Example 1 was subjected to theesterification with the use of 210 grams commercial butyric acid insteadof 130 grams acetic acid. The addition of butyric acid during theesterification was not necessary. A water-white ester boiling between142 and 154 C. at mm. Hg and having the following characteristics wasobtained:

Acid number; 0. Ester number 234 (calculated: 235). Hydroxyl number 0.Density at 20 C 0.947. Refractive index, 12 1.4631. Molecular weight 241(calculated: 238). Pour point 70 C. Flash point 129 C. Viscosity index152.

Example 4 The valeric acid ester and caproic acid ester were produced inthe manner described in the preceding examples with the use ofcommercial valeric acid and caproic acid, respectively. To remove theexcess acid, the raw esters were washed, prior to the washing withwater, with a 2% caustic soda solution until the acid number had droppedto 0. At 143 C. and 5 mm. Hg a valeric acid ester was obtained which hadthe following characteristics:

Acid number 0.

Ester number 220 (calculated: 222). Hydroxyl number 0.

Density at 20 C 0.939.

Refractive index, r2 1.4612.

Molecular weight 253 (calculated: 252). Pour point 68 C.

Flash point 144 C.

Viscosity index 148.

The corresponding caproic acid ester which had a boiling point of 138C.l40 C. at 0.8 mm. Hg had the following characteristics:

Acid number 0. Ester number 202 (calculated: 210). Hydroxyl number -1 0.Density at 20 C 0.934. Refractive index, n 1.4631. Molecular weight 263(calculated: 266). Pour point -71 C. Flash point 153 C. Viscosity index157.

Example 5 200 grams terp-ane methylol were boiled with 242 gms. of Cfatty acid, which had beenproduced by treating a branched C alcoholhaving a pour point of -29 C.

with alkali at melting temperature, in the presence of cc. toluene and 1cc. concentrated hydrochloric acid under a reflux condenser with Waterseparation in the manner described in Example 1. After two hours, theraw product was washed with water to remove the hydrochloric acid anddistilled. After the removal of the toluene and of the excess terpanemethylol, there was obtained as the main fraction at 208210 C. and 0.8mm. Hg a viscous ester which had the following characteristics:

228 grams of a branched C alcohol having the characteristics Hydroxylnumber 230 Pour point C 30 Density at 20 C 0.840

202 gms. of terpane carboxylic acid produced by treating terpanemethylal with alkali at melting. temperature and having the followingcharacteristics:

Acid number 298 (calculated: 308). Density at 20 C 1.015.

Refractive index, 11 1.4778.

Pour point 22C.

200 cc. toluene and 3 gms. of toluene-sulfonic acid were boiled for 3hours at a reflux condenser with water separation. Following this, theraw product was washed at first with a 2% caustic soda solution untilthe acid number had disappeared, and then with 50% ethyl alcohol to washout dissolved soaps. Then it was distilled. At 208 217 C. and 1 mm. Hgthe pure ester was obtained which had the following characteristics:

Acid number 0.

Ester number 129 (calculated: 143). Hydroxyl number 0.

Density at 20 C 0.907.

Refractive index, 11 1.4670.

Molecular weight 398 (calculated: 392). Four point -60 C.

Flash point 195 C.

Viscosity at 50 C 2.24 Engler degrees. Viscosity index 96.

The flash point of this ester was lowered by 23 C. and the viscosityindex was lower by 36 units as compared with the corresponding esterprepared in accordance with Example 5.

Example 7 150 gms. of a synthetic branched C alcohol having thecharacteristics:

Molecular weight 186.

Hydroxyl number 300.

Pour point -53 C.

Boiling range 131134 C. at 10 mm. Hg.

were esterified with 180 grns. of terpane carboxylic acid in accordancewith Example 6. The ester obtained had the following characteristics:

Density at 20 C 0.918.

Refractive index, n 1.4653.

Ester number 162 (calculated: Hydroxyl number 0.

Acid number 0.

Molecular weight 351 (calculated: 350). Pour point 59 C.

Flash point 185 C.

Viscosity at 30 C 2.96 Engler degrees. Viscosity at 50 C 1.87 Englerdegrees. Viscosity index 125 Engler degrees.

The same C alcohol was subjected to the treatment with alkali at meltingtemperature and then to a treatment with acid, thereby producing thebranched C fatty acid which had the following characteristics:

Density at 20 C 0.891.

Refractive index, n L 1.4387.

Acid number 278 (calculated: 279). Four point 40" C.

222 gms. (1.11 mols) of this acid were esterified with 151 gms. (0.9mol) terpane methylol with the addition of toluene as described in thepreceding examples. After the separation of 16 cc. (0.89 mol) of water,the excess acid was removed by washing with 5% aqueous caustic sodasolution and 50% ethanol and the raw ester was fractionated. The esterthus obtained in the pure form had the following characteristics:

Density at 20 C 0.910. Refractive index, r1 1.4641. Ester number 162(calculated: 160). Hydroxyl number 0.1. Molecular weight 350.5(calculated: 350). Four point 64 C. Flash point 199 C. Viscosity at 30 C2.72 Engler degrees. Viscosity at 5 0 C 1.775 Engler degrees. Viscosityindex 129.

Example 8 370 grams (2.2 mols) terpane methylol C I-I 0 were boiled with564 grams (2 mols) commercial oleic acid and 180 cc. commercial toluene,to which 3 grams p-toluene-sulfonic acid had been added, for 2 hours ina 2 liter round-bottomed flask with reflux condenser and waterseparation. During this time, 36 cc. of water which, by azeotropicdistillation of the toluene, had been removed from the esterificationmixture, accumulated in the water separating vessel. After thetermination of the water separation, the toluene was removed from theesterification mixture by distillation under atmospheric pressure.Following this, the excess terpanol was removed by distillation underreduced pressure of about 10-1 mm. Hg at a temperature of 100130 C.

The residue from distillation was now mixed with 8.6 grams magnesia anddistilled at 0.4 mm. Hg and bottom temperatures of 225260 C. in ahigh-vacuum apparatus with short distilling paths as, for example, in a2 liter flask with ground top to which a downwardly angled, air-cooledground piece of large diameter was attached which was connected to a 2liter receiver with ground top. There were obtained 820 grams of anester which was only weakly yellowish colored and had the followingcharacteristics:

Density at C 0.905. Refractive index, n 1.4720. Molecular weight 432(calculated: 432). Pour point 28 C. Flash point 227 C. Viscosity at 50 C2.17 Engler degrees. Viscosity index 140. Color according toLudwigshafen iodine number scale Below 4. Acid number 0.1. Ester number131 (calculated: 130) Iodine number 5'7 (calculated: 59). Hydroxylnumber 3. Carbonyl number 0.

To remove the low hydroxyl number still present, the ester describedabove, if desired, may be distilled once more as first runnings. Thissecond distillation, however, is efiected with the addition of 5-8 gramszinc oxide instead of magnesia. The purpose of adding magnesia in thefirst distillation is to combine the acid still present in the raw esteras, for example, p-toluene-sulfonic acid and small amounts ofunesterified oleic acid. This results, however, in a slight estercleavage which becomes evident in the ester distilled only once by thepresent hydroxyl number of 3. The addition of zinc oxide in the seconddistillation does not effect an additional ester cleavage but reducesthe darkening of the color of the ester distillates. The change of thephysical data of the ester by the removal of the hydroxyl number is onlynegligible.

Example 9 294 grams (1.75 mols) terpane methylol were esterified with316 grams (1.93 mols) trichloroacetic acid with the addition of 2 gramsp-toluene-sulfonic acid and cc. benzene in the manner described inExample 8. After the termination of the water separation, the excesschloroacetic acid was removed from the esterification mixture by washingthe same five times with water, and then the benzene added as theentraining agent for the water was driven ofif by distillation. Theremaining raw ester was fractionated at about 5 mm. Hg. At 156-158 C.,an ester fraction was obtained which had the following characteristics:

Density at 20 C 1.203. Refractive index, ri 1.4793. Molecular weight 307(calculated: 313.5). Chlorine content 33.5% (calculated: 34.1%). Flashpoint 160 C. Pour point 5'5 C. Turbidity point 40 C. Viscosity at 30 C15.9 cst. Viscosity at 80 C 3.59 cst. Viscosity at 50 C 7.3 cst.Viscosity index 135. Color Water-white.

Example 10 252 grams terpane methylol (1.5 mols) were esterified, in themanner described in the preceding example, with 151 grams pure lacticacid (1.68 mols) with the addition of cc. benzene and 1.5 gramsp-toluene-sulfonic acid. After the termination of the water separation,the excess lactic acid, similar to Example 9, was removed from the estermixture by washing the same five times with water, and then the benzenewas driven off. The remaining raw ester was fractionated at 10 mm. Hg.At a temperature between and 173 C., a fractionated ester was obtainedwhich had the following characteristics:

1. A low pour-point oil suitable as a low-temperature lubricating oil,comprising a monocarboxylic acid-monohydric alcohol ester having aterpane compound, obtained by the catalytic addition of carbon monoxideand hydrogen to the alkylene double bond of a terpene hydrocarboncontaining an alkylene radical, as one of the monocarboxylic acid andmonohydric alcohol compoments, and an aliphatic compound as the othercomponent.

2. Process for the production of low pour-point oils, which comprises incombination the aldehydic catalytic addition of carbon monoxide andhydrogen to the aliphatic double bond of a terpene hydrocarboncontaining an aliphatic radical with olefinic unsaturation to form thecorresponding aliphatic aldehyde thereof, the treatment of said aldehydewith a member selected from the group consisting of oxygen and hydrogento form the corresponding terpane carboxylic acid and terpane alcoholrespectively, and the esterification of said terpane With an aliphaticcompound, one of said terpane and aliphatic compound being a carboxylicacid and the other being an alcohol, and recovering an oil suitable as alow-temperature lubricating oil.

3. Process for the production of low pour-point oils, which comprises incombination the aldehydic catalytic addition of carbon monoxide andhydrogen to the alkylene double bond of a terpene hydrocarbon containingan alkylene radical to form the corresponding alkyl aldehyde thereof,the treatment of said aldehyde with a member selected from the groupconsisting of oxygen and hydrogen to form the corresponding terpanemonocarboxylic acid and terpane monohydric alcohol respectively, and theesterification of said terpane with an aliphatic compound, one of saidterpane and aliphatic compound being a monocarboxylic acid and the otherbeing a monohydric alcohol, and recovering an oil suitable as alow-temperature lubricating oil.

4. A low pour-point oil suitable as a low-temperature lubricating oil,comprising a carboxylic acid-alcohol ester having a terpane compound,obtained by the catalytic addition of carbon monoxide and hydrogen tothe aliphatic double bond of a terpene hydrocarbon containing analiphatic radical with olefinic unsaturation, as one of the carboxylicacid and alcohol components, and an aliphatic compound as the othercomponent.

5. Oil according to claim 4, in which said aliphatic compound containsfrom 2 to 20 carbon atoms.

6. Oil according to claim 5, in which said aliphatic compound is abranched chain monofunctional aliphatic compound containing more than 8carbon atoms.

7. Oil according to claim 4, in which said ester is a terpanemethylol-fatty acid ester.

8. Oil according to claim 4, in which said ester is a terpane carboxylicacid-aliphatic alcohol ester.

9. Process according to claim 2, in which said aliphatic compoundcontains from 2 to 20 carbon atoms.

10. Process according to claim 9, in which said aliphatic compound is abranched chain monofunctional aliphatic compound having a chain lengthof more than 8 carbon atoms.

11. Process according to claim 2, in which terpane methylol isesterified with a fatty acid.

12. Process according to claim 2, in which terpane carboxylic acid isesterified with an aliphatic alcohol.

13. Oil according to claim 5, in which said aliphatic compound containsfrom 4 to 18 carbon atoms.

14. Process according to claim 9, in which said aliphatic compoundcontains from 4 to 18 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS900,316 Shukofi Oct. 6, 1908 907,941 Zietschel Dec. 29, 1908 969,420Sulzberger Sept. 6, 1910 2,501,199 Wearn et a1. Mar. 21, 1950 2,668,177Corbett et a1. Feb. 2, 1954 2,705,724 Cottle et al. Apr. 5, 1955 OTHERREFERENCES Fieser et al.: Organic Chemistry, 1944, page 984.

Lo Cicero et al.: I.A.C.S., vol. 74, No. 8, 1952, pp. 20942097.

Heilbron: Dictionary of Organic Compounds, 1953, page 826 (Norborneol).

1. A LOW POUR-POINT OIL SUITABLE AS A LOW-TEMPERATURE LUBRICATING OIL,COMPRISING A MONOCARBOXYLIC ACID-MONOHYDRIC ALCOHOL ESTER HAVING ATERPANE COMPOUND, OBTAINED BY THE CATALYTIC ADDITION OF CARBON MONOXIDEAND HYDROGEN TO THE ALKYLENE DOUBLE BOND OF A TERPENE HYDROCARBONCONTAINING AN ALKYLENE RADICAL, AS ONE OF THE MONOCARBOXYLIC ACID ANDMONOHYDRIC ALCOHOL COMPOMENTS, AND AN ALIPHATIC COMPOUND AS THE OTHERCOMPONENT.